Invasive prenatal diagnostic procedures 2005

Invasive Prenatal Diagnostic Testing for Aneuploidies in Singleton Pregnancies: A Comparative Review of Major Guidelines

Sophisticated screening protocols for genetic abnormalities constitute an important component of current prenatal care, aiming to identify high-risk pregnancies and offer appropriate counseling to parents regarding their options. Definite prenatal diagnosis is only possible by invasive prenatal diagnostic testing (IPDT), mainly including amniocentesis and chorionic villous sampling (CVS). The aim of this comparative review was to summarize and compare the existing recommendations on IPDT from the most influential guidelines. All the reviewed guidelines highlight that IPDT is indicated based on a positive screening test rather than maternal age alone. Other indications arise from medical history and sonography, with significant variations identified between the guidelines. The earlier time for amniocentesis is unequivocally set at ≥15 gestational weeks, whereas for CVS, the earlier limit varies from ≥10 to ≥11 weeks. Certain technical aspects and the overall approach demonstrate significant differences. Periprocedural management regarding Rhesus alloimmunization, virologic status and use of anesthesia or antibiotics are either inconsistent or insufficiently addressed. The synthesis of an evidence-based algorithm for IPDT is of crucial importance to healthcare professionals implicated in prenatal care to avoid unnecessary interventions without compromising optimal prenatal care.

Clinical Application of Noninvasive Prenatal Testing for Pregnant Women with Assisted Reproductive Pregnancy

Objective

This paper analyzes the clinical significance of noninvasive prenatal testing (NIPT) for fetal chromosome aneuploidy in the screening of in vitro fertilization–embryo transfer (IVF) pregnancies.

Methods

The study subjects consisted of 3163 IVF-pregnant women who underwent NIPT at the Women’s Hospital, School of Medicine, Zhejiang University and Taizhou Hospital, Zhejiang Province from February 2015 to June 2019. Fetal or neonatal karyotype analysis was carried out in high-risk patients, with subsequent follow-up on pregnancy outcomes.

Results

NIPT results of 3163 pregnant women suggested 20 cases of high-risk fetal chromosome aneuploidy, of which 2185 cases were a single pregnancy. Of the 13 cases of high-risk chromosome aneuploidy in single pregnancies, seven were true positive, and six were false positive according to fetal or newborn chromosomal karyotype diagnosis. Twin pregnancies accounted for 978 cases in which NIPT indicated seven cases of high-risk chromosome aneuploidy; six of these cases were true positive, and one case was false positive according to fetal or newborn chromosomal karyotype diagnosis. The specificity, positive predictive value, and false-positive rate of trisomy 21 syndrome in IVF single embryo NIPT were 99.86%, 62.5%, and 0.14%, respectively. The specificity, positive predictive value, and false-positive rate of trisomy 18 syndrome were 99.95%, 66.67%, and 0.05%, respectively. The specificity of trisomy 13 syndrome was 99.91%, and the false-positive rate was 0.09%. The specificity of trisomy 21 syndrome in IVF twin NIPT was 99.89%, the positive predictive value was 83.33%, and the false-positive rate was 0.11%. The specificity and positive predictive value of fetal trisomy 18 syndrome were 100.00%, and the false-positive rate of it were 0.00%. Sensitivity and false-negative rates were 100% in all cases.

Conclusion

NIPT is an ideal prenatal test for IVF-pregnant women due to its high sensitivity and specificity in screening for fetal aneuploidy.

Droplet-based digital PCR for non-invasive prenatal genetic diagnosis of α and β-thalassemia

Non-invasive prenatal diagnosis (NIPD) of isolated cell-free DNA from maternal plasma has been applied to detect monogenic diseases in the fetus. Droplet digital PCR (ddPCR) is a sensitive and quantitative technique for NIPD. In the present study, the development and evaluation of ddPCR-based assays for common α and β-thalassemia variants amongst the Asian population was described; specifically, Southeast Asian (SEA) deletion, HbE, and 41/42 (-CTTT). SEA is caused by deletion of a 20 kb region surrounding the α-globin gene, whilst HbE and 41/42 (-CTTT) are caused by point mutations on the β-globin gene. Cell-free DNA samples from 46 singleton pregnant women who were carriers of these mutations were isolated and quantified using ddPCR with specially designed probes for each target allele. Allelic copy number calculation and likelihood ratio tests were used to classify fetal genotypes. Classification performances were evaluated against ground truth fetal genotypes obtained from conventional amniocentesis. Copy number variation analysis of SEA deletion accurately classified fetal genotypes in 20 out of 22 cases with an area under the receiver operating characteristic curve of 0.98 for detecting Hb Bart's hydrops fetalis. For HbE cases, 10 out of 16 samples were correctly classified, and three were inconclusive. For 41/42 (-CTTT) cases, 2 out of 8 were correctly classified, and four were inconclusive. The correct genotype was not rejected in any inconclusive case and may be resolved with additional ddPCR experiments. These results indicate that ddPCR-based analysis of maternal plasma can become an accurate and effective NIPD for SEA deletion α-(0) thalassemia. Although the performance of ddPCR on HbE and 41/42 (-CTTT) mutations were not sufficient for clinical application, these results may serve as a foundation for future works in this field.

GC-MS analysis of seven metabolites for the screening of pregnant women with Down Syndrome fetuses

Down Syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. Metabolomics is identification and quantification of small-molecule metabolites (molecular weight <1000 Da) in tissues, cells and physiological fluids within a certain period time. Metabolites are intermediate products of various types of biochemical reactions that participate in bonding metabolic pathways. In this study, metabolites such as 2-Hydroxybutyric acid, 3-Hydroxybutyric acid, β-Hydroxyisovaleric acid, Uracil, Glutamic acid, Maltose and Melezitose were chosen as the possible determinants/markers for the prenatal screening of Down Syndrome. Quantitative analysis of the metabolites conducted by GCMS method using 5 % phenyl / 95 % dimethylpolysiloxane (30 m ×0.25 mm, 0.25 μm film thickness) capillary column. The oven temperature was held constant at 60 °C for 1 min and ramped at 10 °C /min to 200 °C then ramped at 30 °C/min to 320 °C and hold for 6 min before cool-down, as helium mobile phase and flow rate of 2.8 mL/min and adding Myristic acid-d27 as an internal standard. Our method was validated by parameters of system suitability, stability, linearity, sensitivity, accuracy, precision, selectivity, robustness and ruggedness. The developed and validated method was applied to plasma samples taken from pregnant women with Down Syndrome (study group) and euploid fetuses (healthy group). The levels of these seven metabolites are statistically different (p < 0.05 for all) between the groups. It can be concluded that these relevant metabolites might be used for the prenatal screening of Down Syndrome.

Evaluation of droplet digital PCR for non-invasive prenatal diagnosis of phenylketonuria

This study was carried out to establish a non-invasive prenatal diagnosis method for phenylketonuria (PKU) based on droplet digital PCR (ddPCR) and to evaluate its accuracy by comparison with conventional invasive diagnostic methods. A total of 24 PKU pedigrees that required prenatal diagnosis were studied, in which the genetic mutations in the probands and parents were unambiguous. Prenatal diagnosis of sibling fetuses was performed using traditional invasive prenatal diagnostic methods as a standard. At the same time, cell-free DNA (cfDNA) was extracted from maternal plasma and the fetal genes contained within were typed and quantified using ddPCR method. Invasive prenatal diagnosis determined that 3 of the 24 fetuses were affected, 8 of them were normal, and 13 were heterozygous carriers of pathogenic mutations. Successful non-invasive prenatal diagnosis analysis of PAH gene mutations was performed for 8 of the families using ddPCR method. Non-invasive prenatal diagnosis results were consistent with the results of the invasive prenatal diagnoses and no false positive or false negative results were found. In conclusion, this study is the first to establish non-invasive prenatal diagnosis of PKU based on ddPCR. The method showed high sensitivity and specificity from cfDNA, indicating that ddPCR is a reliable non-invasive prenatal diagnosis tool for PKU diagnosis. Graphical abstract.

The benefits and limitations of cell-free DNA screening for 47, XXY (Klinefelter syndrome)

OBJECTIVE

The purpose of this paper is to provide an overview of the 47, XXY syndrome, which is the most commonly occurring X and Y chromosomal variation. This paper seeks to review what is currently known of noninvasive prenatal testing (NIPT) and 47, XXY and investigate potential risks and benefits of prenatal identification.

METHOD

A literature review of NIPT and 47, XXY was performed to identify limitations of current NIPT techniques.

RESULTS

As NIPT becomes an increasingly more routine procedure, prenatal findings of 47, XXY may increase. Awareness of this disorder and appropriate genetic counseling is necessary.

CONCLUSION

X and Y chromosomal variations will be identified through this screening, and the benefits and limitations to this finding need to be thoughtfully considered. © 2017 John Wiley & Sons, Ltd.

Steroid 21-hydroxylase deficiency in congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) refers to a group of inherited genetic disorders involving deficiencies in enzymes that convert cholesterol to cortisol within the adrenal cortex. There are five key enzymes involved in the production of cortisol. Of these key enzymes, deficiency of 21-hydroxylase is the most commonly defective enzyme leading to CAH representing more than 90% of cases. The low adrenal cortisol levels associated with CAH affects the hypothalamic-pituitary-adrenal negative feedback system leading to increased pituitary adrenocorticotropic hormone (ACTH) production, which overstimulates the adrenal cortex in an attempt to increase cortisol production resulting in a hyperplastic adrenal cortex. The deficiency of enzyme 21-hydroxylase results from mutations or deletions in the CYP21A2 gene found on chromosome 6p. The disorder is transmitted as an autosomal recessive pattern and specific mutations may be correlated to enzymatic compromise of varying degrees, leading to the clinical manifestation of 21-hydroxylase deficiency (21-OHD) CAH.

Cell-free DNA: Comparison of Technologies

Cell-free fetal DNA screening for Down syndrome has gained rapid acceptance over the past few years with increasing market penetration. Three main laboratory methodologies are currently used: a massive parallel shotgun sequencing (MPSS), a targeted massive parallel sequencing (t-MPS) and a single nucleotide polymorphism (SNP) based approach. Although each of these technologies has its own advantages and disadvantages, the performance of all was shown to be comparable and superior to that of traditional first-trimester screening for the detection of trisomy 21 in a routine prenatal population. Differences in performance were predominantly shown for chromosomal anomalies other than trisomy 21. Understanding the limitations and benefits of each technology is essential for proper counseling to patients. These technologies, as well as few investigational technologies described in this review, carry a great potential beyond screening for the common aneuploidies.

Bisulfite Conversion of DNA: Performance Comparison of Different Kits and Methylation Quantitation of Epigenetic Biomarkers that Have the Potential to Be Used in Non-Invasive Prenatal Testing

INTRODUCTION

Epigenetic alterations, including DNA methylation, play an important role in the regulation of gene expression. Several methods exist for evaluating DNA methylation, but bisulfite sequencing remains the gold standard by which base-pair resolution of CpG methylation is achieved. The challenge of the method is that the desired outcome (conversion of unmethylated cytosines) positively correlates with the undesired side effects (DNA degradation and inappropriate conversion), thus several commercial kits try to adjust a balance between the two. The aim of this study was to compare the performance of four bisulfite conversion kits [Premium Bisulfite kit (Diagenode), EpiTect Bisulfite kit (Qiagen), MethylEdge Bisulfite Conversion System (Promega) and BisulFlash DNA Modification kit (Epigentek)] regarding conversion efficiency, DNA degradation and conversion specificity.

METHODS

Performance was tested by combining fully methylated and fully unmethylated λ-DNA controls in a series of spikes by means of Sanger sequencing (0%, 25%, 50% and 100% methylated spikes) and Next-Generation Sequencing (0%, 3%, 5%, 7%, 10%, 25%, 50% and 100% methylated spikes). We also studied the methylation status of two of our previously published differentially methylated regions (DMRs) at base resolution by using spikes of chorionic villus sample in whole blood.

RESULTS

The kits studied showed different but comparable results regarding DNA degradation, conversion efficiency and conversion specificity. However, the best performance was observed with the MethylEdge Bisulfite Conversion System (Promega) followed by the Premium Bisulfite kit (Diagenode). The DMRs, EP6 and EP10, were confirmed to be hypermethylated in the CVS and hypomethylated in whole blood.

CONCLUSION

Our findings indicate that the MethylEdge Bisulfite Conversion System (Promega) was shown to have the best performance among the kits. In addition, the methylation level of two of our DMRs, EP6 and EP10, was confirmed. Finally, we showed that bisulfite amplicon sequencing is a suitable approach for methylation analysis of targeted regions.

A transcervical chorionic villus sampling model for teaching

We sought to create a transcervical chorionic villus sampling model for teaching that would mimic a lifelike model. A model was created using silicone resembling the maternal interface. A cervix with an endocervical canal able to accommodate a catheter and a vagina was also created. Tap water was used as the amniotic fluid. Chorionic villus sampling was accomplished using this model with the actual ultrasound machines and environment as in the real model. This simulator allowed placental placement in different locations to increase the difficulty level as well as angulations and catheter handling. Given the low cost (less than $200), this model could be used indefinitely in a relaxed and controlled environment.

Non-invasive prenatal diagnosis by massively parallel sequencing of maternal plasma DNA

The presence of foetal DNA in the plasma of pregnant women has opened up new possibilities for non-invasive prenatal diagnosis. The use of circulating foetal DNA for the non-invasive prenatal detection of foetal chromosomal aneuploidies is challenging as foetal DNA represents a minor fraction of maternal plasma DNA. In 2007, it was shown that single molecule counting methods would allow the detection of the presence of a trisomic foetus, as long as enough molecules were counted. With the advent of massively parallel sequencing, millions or billions of DNA molecules can be readily counted. Using massively parallel sequencing, foetal trisomies 21, 13 and 18 have been detected from maternal plasma. Recently, large-scale clinical studies have validated the robustness of this approach for the prenatal detection of foetal chromosomal aneuploidies. A proof-of-concept study has also shown that a genome-wide genetic and mutational map of a foetus can be constructed from the maternal plasma DNA sequencing data. These developments suggest that the analysis of foetal DNA in maternal plasma would play an increasingly important role in future obstetrics practice. It is thus a priority that the ethical, social and legal issues regarding this technology be systematically studied.

Cell-free fetal DNA testing for fetal aneuploidy and beyond: clinical integration challenges in the US context

The recent release of new, non-invasive prenatal tests for fetal aneuploidy using cell-free fetal DNA (cffDNA) has been hailed as a revolution in prenatal testing and has triggered significant commercial interest in the field. Ongoing research portends the arrival of a wide range of cffDNA tests. However, it is not yet clear how these tests will be integrated into well-established prenatal testing strategies in the USA, as the timing of such testing and the degree to which new non-invasive tests will supplement or replace existing screening and diagnostic tools remain uncertain. We argue that there is an urgent need for policy-makers, regulators and professional societies to provide guidance on the most efficient and ethical manner for such tests to be introduced into clinical practice in the USA.

Genomic analysis of fetal nucleic acids in maternal blood

The 15 years since the discovery of fetal DNA in maternal plasma have witnessed remarkable developments in noninvasive prenatal diagnosis. An understanding of biological parameters governing this phenomenon, such as the concentration and molecular size of circulating fetal DNA, has guided its diagnostic applications. Early efforts focused on the detection of paternally inherited sequences, which were absent in the maternal genome, in maternal plasma. Recent developments in precise measurement technologies such as digital polymerase chain reaction (PCR) have allowed the detection of minute allelic imbalances in plasma and have catalyzed analysis of single-gene disorders such as the hemoglobinopathies and hemophilia. The advent of massively parallel sequencing has enabled the robust detection of fetal trisomies in maternal plasma. Recent proof-of-concept studies have detected a chromosomal translocation and a microdeletion and have deduced a genome-wide genetic map of a fetus from maternal plasma. Understanding the ethical, legal, and social aspects in light of such rapid developments is thus a priority for future research.

Optimal Detection of Fetal Chromosomal Abnormalities by Massively Parallel DNA Sequencing of Cell-Free Fetal DNA from Maternal Blood

BACKGROUND

Massively parallel DNA sequencing of cell-free fetal DNA from maternal blood can detect fetal chromosomal abnormalities. Although existing algorithms focus on the detection of fetal trisomy 21 (T21), these same algorithms have difficulty detecting trisomy 18 (T18).

METHODS

Blood samples were collected from 1014 patients at 13 US clinic locations before they underwent an invasive prenatal procedure. All samples were processed to plasma, and the DNA extracted from 119 samples underwent massively parallel DNA sequencing. Fifty-three sequenced samples came from women with an abnormal fetal karyotype. To minimize the intra- and interrun sequencing variation, we developed an optimized algorithm by using normalized chromosome values (NCVs) from the sequencing data on a training set of 71 samples with 26 abnormal karyotypes. The classification process was then evaluated on an independent test set of 48 samples with 27 abnormal karyotypes.

RESULTS

Mapped sites for chromosomes of interest in the sequencing data from the training set were normalized individually by calculating the ratio of the number of sites on the specified chromosome to the number of sites observed on an optimized normalizing chromosome (or chromosome set). Threshold values for trisomy or sex chromosome classification were then established for all chromosomes of interest, and a classification schema was defined. Sequencing of the independent test set led to 100% correct classification of T21 (13 of 13) and T18 (8 of 8) samples. Other chromosomal abnormalities were also identified.

CONCLUSION

Massively parallel sequencing is capable of detecting multiple fetal chromosomal abnormalities from maternal plasma when an optimized algorithm is used.

Noninvasive prenatal diagnosis: 2010

Looking for fetal cells and now nucleic acids has been the holy grail of prenatal diagnosis for more than a century. The use of noninvasive diagnostics has potential far beyond aneuploidy; in fact, its use for Rhesus disease is already commonplace in Europe. Accurate segregation of fetal cells from maternal cells or identification of cell-free fetal (cff) DNA or RNA is critical to the development of fetal cells as a screening or diagnostic prenatal technique. The large number of approaches that have been used is testimony to the fact that none of them have been particularly successful. This article discusses the current status and challenges of noninvasive prenatal diagnosis.

Fetal androgen exposure and pragmatic language ability of girls in middle childhood: implications for the extreme male-brain theory of autism

Prenatal exposure to testosterone has been shown to affect fetal brain maturation as well as postnatal cognition and behavior in animal studies. Although there are well-established sex-differences in the use of social communication (or 'pragmatic language') in humans, there has been limited investigation of the association between fetal testosterone exposure and postnatal pragmatic language ability. In this prospective study, pragmatic language skills, assessed using a pragmatic language score (PLS), were measured in 78 girls aged 10 years and correlated with testosterone levels in umbilical cord blood. A measure of the biologically active, 'free' fraction of testosterone, the free androgen index (FAI), was positively correlated with the PLS (R=.3). Regression analyses showed that the FAI was a significant, positive predictor of pragmatic language difficulties in girls after controlling for maternal and infant-health variables (B=0.02, 95% confidence interval=0.01-0.04, p=0.02). This is the first prospective study to identify an association between early life testosterone exposure and pragmatic language difficulties in girls. These novel findings are discussed with reference to the 'extreme male-brain' theory of autism.

Amniovacucentesis vs standard syringe technique for amniocentesis: experience with 1219 cases

OBJECTIVE

The aim of the study was to compare amniovacucentesis to the usual syringe use for amniotic fluid aspiration.

STUDY DESIGN

We compared 2 groups of procedures: 1117 amniocenteses performed with the usual syringe technique and 1219 amniovacucenteses.

RESULTS

The numbers of needle insertions, unsuccessful amniocyte cultures, and miscarriage up to 21 days after the procedure were statistically not significant (P>.01) comparing the 2 techniques.

CONCLUSION

The vacuum tube serves as an automated aspiration tool alternative. The major subjective differences between the 2 methods are the operator's comfort and dexterity during sampling and the absence of an extra manipulation of the amniotic fluid after aspiration.

Some ethical issues in the prenatal diagnosis of sickle cell anaemia

Sickle cell anaemia (SCA) is the most common form of haemoglobinopathy in Nigeria affecting 1-3% of the population and it is associated with physical, psychosocial and emotional suffering. Prenatal diagnosis (PND) and genetic counseling are ways of preventing the spread of the disease; however these means of prevention are associated with many ethical dilemmas. Ethical issues discussed in this paper include the safety of the procedures used in obtaining tissue sample for prenatal diagnosis, abortion of affected fetuses and the question of genetic selection. Finally, the ethical implications of genetic counseling and issues relating to the principle of justice in healthcare are highlighted.

Is screening for fetal anomalies reliable in HIV-infected pregnant women? A multicentre study

OBJECTIVE

To assess the impact of HIV infection on the reliability of the first-trimester screening for Down syndrome, using free beta-human chorionic gonadotrophin, pregnancy-associated plasma protein-A and fetal nuchal translucency, and of the second-trimester screening for neural tube defects, using alpha-fetoprotein.

PATIENTS AND METHODS

Multicentre study comparing the multiples of the median of markers for Down syndrome and neural tube defect screening among 214 HIV-infected pregnant women and 856 HIV-negative controls undergoing a first-trimester Down syndrome screening test, and 209 HIV-positive women and 836 HIV-negative controls with a risk evaluation for neural tube defect. The influence of treatment, chronic hepatitis and HIV disease characteristics were also evaluated.

RESULTS

Multiples of the median medians for pregnancy-associated plasma protein-A and beta-human chorionic gonadotrophin were lower in HIV-positive women than controls (0.88 vs. 1.05 and 0.84 vs. 1.09, respectively; P < 0.005), but these differences had no impact on risk estimation; no differences were observed for the other markers. No association was found between HIV disease characteristics, antiretroviral treatment use at the time of screening or chronic hepatitis and marker levels.

CONCLUSION

Screening for Down syndrome during the first trimester and for neural tube defect during the second trimester is accurate for HIV-infected women and should be offered, similar to HIV-negative women.

Clinical consequences of an increasing trend of preferential use of cultured villi for molecular diagnosis by CVS

OBJECTIVE

To compare the use of uncultured versus cultured villus cells for DNA-based prenatal diagnosis.

METHODS

A retrospective review of molecular testing of chorionic villus sampling (CVS) cases from 1988-2007. Method of analysis, gestational age (GA) at CVS and at diagnosis, time from procedure to results, results of maternal contamination studies, and the laboratory employed were abstracted from patient charts. Trends in laboratory practices over time were analyzed.

RESULTS

Time from CVS to diagnosis was longer when cultured cells were used. Average GA at diagnosis was 14-6/7 weeks with cultured cells vs 13-0/7 weeks with uncultured villi (p < 0.001). Recently, laboratories are more frequently requiring cultured cells, resulting in significantly greater delays in time to diagnosis and GA at results.

CONCLUSIONS

'Direct' DNA extraction saves 2 weeks from CVS to results. More women are afforded the option of an earlier, safer pregnancy termination if uncultured villi are used for molecular diagnosis. Implementation of standardized DNA extraction protocols and sample-size requirements can optimize the use of uncultured villi for molecular prenatal diagnosis. Increased awareness of the importance of rapid results and the advantages of 'direct' DNA extraction from uncultured villi can lead to improvements that are of clinical significance for patients undergoing early prenatal diagnosis.

A comparative analysis of cartilage engineered from different perinatal mesenchymal progenitor cells

We sought to compare engineered cartilaginous constructs derived from different perinatal mesenchymal progenitor cell (MPC) sources. Ovine MPCs isolated from amniotic fluid (AF, n = 8), neonatal bone marrow (BM, n = 6), and preterm umbilical cord blood (CB, n = 12) were expanded and comparably seeded onto synthetic scaffolds. Constructs were maintained in chondrogenic media containing transforming growth factor-beta. After 12-15 weeks, specimens were compared with native fetal hyaline and elastic cartilage by gross inspection, histology, immunohistochemistry, and quantitative extracellular matrix (ECM) assays. MPCs from AF proliferated significantly faster ex vivo when compared to MPCs from the other sources. Chondrogenic differentiation was evident in all groups, as shown by toluidine blue staining and expression of aggrecan, cartilage proteoglycan link protein, and collagen type II. Quantitatively, all engineered specimens had significantly lower levels of glycosaminoglycans than native hyaline cartilage. Elastin levels in AF-based constructs (156.0 +/- 120.4 microg/mg) were comparable to that of native elastic cartilage (235.8 +/- 54.2 microg/mg), both of which were significantly higher than in BM- and CB-based specimens. We conclude that the ECM profile of cartilage engineered from perinatal MPCs is highly dependent on cell source. ECM peculiarities should be considered when designing the optimal cartilaginous bioprosthesis for use in perinatal surgical reconstruction.

Outcome of chromosomally abnormal pregnancies in Lebanon: obstetricians' roles during and after prenatal diagnosis

OBJECTIVES

To better understand obstetrician experiences in Lebanon when disclosing abnormal amniocentesis results.

METHODS

Structured interviews with 38 obstetricians identified as caregivers from the American University of Beirut Medical Center Cytogenetics Laboratory database of patients with abnormal amniocentesis results between 1999 and 2005.

RESULTS

Obstetricians were primarily male, Christian, and with an average of 14 years of experience. They reported doing most pre-amniocentesis counseling, including discussion of risk for common autosomal aneuplodies (95%), and procedure-related risk (95%). Obstetricians reported that 80% of patients at risk for aneuploidy underwent amniocentesis. The study population reported on 143 abnormal test results (124 autosomal abnormalities). When disclosing results, obstetricians reportedly discussed primarily physical and cognitive features of the diagnosis. They varied in levels of directiveness and comfort in providing information. Our records showed that 59% of pregnancies with sex chromosome abnormalities were terminated compared to 90% of those with autosomal aneuploidies; various reasons were proposed by obstetricians.

CONCLUSIONS

This study is among the few to assess prenatal diagnosis practices in the Middle East, with a focus on the role of the obstetrician. Given the influence of culture and social norms on prenatal decision-making, it remains important to understand the various impacts on clinical practice in many nations.

Nuchal Translucency and First Trimester Risk Assessment

First-trimester risk assessment for fetal aneuploidy using nuchal translucency (NT) measurement is rapidly gaining popularity in the United States. In combination with maternal serum markers in the first trimester, the screening performance is exceptionally good, with detection rates of more than 80% at a screen positive rate of 5%. Recently, the method has been validated for screening for Down syndrome and other aneuploidies in multicenter trials in the United States and elsewhere. Compliance with established criteria for measurement of the NT is essential to achieve uniform reliability and high screening test sensitivity. There is an international consensus about the importance of specific training in the NT examination, conformity to standards of NT measurement, and regular audit for quality assurance. In the United States, the Nuchal Translucency Quality Review program has been developed to administer credentialing and quality review for registered practitioners. The Nuchal Translucency Quality Review credentials signify the proficiency of the sonographer or sonologist in NT measurement and participation in a regular quality assurance audit. We encourage accreditation of clinical sites offering first-trimester risk assessment to ensure the highest quality care.

Awareness and attitude toward prenatal diagnosis of chromosomal abnormalities in patients with no access to legal termination of pregnancy

OBJECTIVE

To analyze variables affecting couples' decision making about prenatal cytogenetic diagnosis in patients with no access to legal termination of pregnancy (TOP).

METHODS

Patients undergoing invasive prenatal diagnosis were anonymously surveyed after counseling and before the procedure. The questionnaire enquired about sociodemographic features, medical history, knowledge of and attitudes toward genetic testing and TOP.

RESULTS

Two genetic units distributed 372 questionnaires. Mean maternal age was 36 +/- 4 years. Access to prenatal genetic counseling was mainly patient's own initiative, or 'self-referral'. Most self-referred patients (87%) considered that 'receiving accurate information' was the main issue. Eighty-one per cent of all couples knew that TOP because of fetal anomalies was not legal. In case of a serious anomaly, 68.2% of patients would contemplate TOP, in spite of the risk of being exposed to an unsafe abortion.

CONCLUSIONS

In many countries, prenatal genetic testing is offered, but TOP is not available. In the present study, although most of the couples who decided to undergo prenatal genetic testing were aware of this, they still chose to perform prenatal diagnosis. The main reason given was to obtain reliable information about fetal condition. Finally, if a fetal chromosomal abnormality were detected, most of them would consider TOP.

Incorporating First-Trimester Down Syndrome Studies Into Prenatal Screening

The National Institute of Child Health and Human Development (NICHD), the Society for Maternal-Fetal Medicine, and the American College of Obstetricians and Gynecologists (ACOG), cosponsored a workshop on December 16-17, 2004, to discuss the evidence for first-trimester Down syndrome screening and to explore the effects of combining first- and second-trimester screening, given the results of recent U.S. trials. The experts evaluated the evidence for offering first-trimester screening to provide individual risk assessment for Down syndrome. First-trimester screening has been demonstrated to provide efficient Down syndrome risk assessment, with a detection rate of 84% (95% confidence interval 80-87%), which is clinically comparable to the second-trimester quadruple screen at a fixed false-positive rate of 5%. The participants at the workshop concluded that at this time there is sufficient evidence to support implementing first-trimester Down syndrome risk assessment in obstetric practice in the United States, provided that certain requirements can be met. These requirements include training and quality control standards for first-trimester nuchal translucency measurement and laboratory assays, access to chorionic villus sampling, and appropriate counseling regarding screening options.